Nonagon
| Regular nonagon (enneagon) | |
|---|---|
 A regular nonagon (enneagon) | |
| Teep | Regular polygon |
| Edges an vertices | 9 |
| Schläfli seembol | {9} |
| Coxeter diagram |    |
| Symmetry group | Dihedral (Dih9), order 2×9 |
| Internal angle (degrees) | 140° |
| Dual polygon | self |
| Properties | convex, cyclic, equilateral, isogonal, isotoxal |
In geometry, a nonagon /ˈnɒnəɡɒn/ (or enneagon /ˈɛniːəɡɒn/) is a nine-sidit regular polygon.
The name "nonagon" is a prefix hybrid formation, frae Laitin (nonus, "ninth" gonon), uised equivalently, attestit already in the 16t century in French nonogone an in Inglis frae the 17t century. The name "enneagon" comes frae Greek enneagonon (εννεα, "nine" γωνον (from γωνία = "corner")), an is arguably mair correct, tho somewhit less common nor "nonagon".
A regular nonagon haes internal angles o 140°. The aurie o a regular nonagon o side length a is gien bi
